Facial saunas are commonly available devices for providing steam to the face, making use of a small bowl in which water, with or without cosmetic additives, is boiled. In Frank, U.S. Pat. No. 3,470,719 and Frank et al. U.S. Pat. No. 4,621,641, among others, prior art liquid heaters of the type useable as facial saunas are disclosed.
Typically, a liquid heater of this type comprises a thermally conductive metal heating bowl, plus heating means, typically electric, for heating the bowl and its contents. In prior art designs the heating means includes a heating element and a terminal board as part of the control of the heating element. Specifically, the heating element may be of a known ceramic type, called a PTC heating element, which is typically positioned against the underside of the bowl. A typical PTC heating element is made of barium titanate, doped with a rare earth such as yttrium, being coated with a conductive surface.
Among the technical design problems that face such liquid heaters, it is desirable to protect the terminal board from excessive heating. This has been done with conventional heat insulation in prior art designs. Also, the plastic housing element must be protected from excess heating.
In accordance with this invention, an improved mounting for the bowl and electric heating system is provided, with the mounting being of increased cost effectiveness and further being capable of providing desired temperature control to both the terminal board and the heating element to economically provide a liquid heater usable as a facial sauna which exhibits optimum operating characteristics and useful life.